The main purpose of this study is to evaluate the safety and efficacy of intravenous MK-0826 as compared to ceftriaxone sodium inplants with serious community-acquired pneumonia. All patients will be treated initially with parenteral study therapy; however, patients in both treatment groups may be offered a common oral antibiotic therapy to complete the duration of treatment. It is expected that MK-0826 will have a favorable clinical response similar to ceftriaxone and will be as safe as deftriaxone based on clinical or laboratory adverse experiences.